Typical methods used to manufacture double-hung replacement windows are extremely time-consuming, expensive and require a high degree of precision. Replacement windows are generally made from extrusions which form the window sash frames and the main frame of the window. These different extrusions are cut to a desired size and subjected to a series of punch press steps to permit the different extrusions to be connected together at right angles. These punch press operations also facilitate insertion of guidepins to attach the sashes to counterweight mechanisms and latch mechanisms to permit removal of the sashes. In the construction of a single double-hung window, literally dozens of punch press and cutting steps are needed. These different punch press steps and cutting steps are very time-consuming.
The punch press equipment is also extremely expensive. Several expensive dies are required to punch press each end of each extrusion, and the punch press equipment itself is extremely expensive. To operate the punch press equipment properly and manufacture a window of precise dimensions requires a careful skilled laborer. Again, this increases the cost of the window.
A second method of manufacturing windows is to use preformed corners to connect different extrusions to form the frame. For example, Collins et al U.S. Pat. No. 4,024,690 discloses the use of preformed plastic corners to form a window. The purpose of this is to maintain a thermal barrier. Construction of the window disclosed in Collins is complex and still requires multiple punch press steps.
Collins et al U.S. Pat. No. 4,037,378 discloses a method of manufacturing the main window frame of a replacement window using molded corners which reduces, but does not totally eliminate, the need to punch press the extrusions forming the main frame of the window. The purpose again is to maintain a thermal barrier. The Collins references fail to disclose or suggest a window construction which would totally eliminate the need for a punch press operation and would substantially reduce the number of saw settings used to cut the extrusions.
Further, Molyneux U.S. Pat. No. 4,136,496 discloses a sub-frame for a window which uses preformed corners. Sub-frames are not comparable to the main frame or sash frame of a window because they typically do not require large channels for counterweights, sashes or glass and do not include any latch mechanisms. The channels, latches and counterweight mechanisms originally necessitated the punch press steps. In other words, two dissimilar extrusions, such as a sill and the vertical extension of the main frame, cannot be assembled directly together without punch pressing one or both of these extrusions.